Driving device comprising a vibrating element



Jan. 2, 1968 R. BESSON 3,360,921

DRIVING DEVICE COMPRISING A VIBRATING ELEMENT Filed Sept. 29, 1965 INVENTQR Rene BESSON United States Patent 3,360,921 DRIVING DEVICE COMPRISING A VIBRATING ELEMENT Ren Besson, Les Loges, Switzerland, assignor to Ebauclres S.A., Neuchatel, Switzerland, a firm of Switzerland Filed Sept. 29, 1965, Ser. No. 491,262 Claims priority, application Switzerland, Oct. 19, 1964, 13,545/64 6 Claims. (Cl. 58-23) The present invention relates to a driving device comprising a vibrating element the vibrations of which are maintained electrically, and has for its object to provide an improved driving device of this kind, more especially though not exclusively for horological applications.

The device according to the present invention comprises a rotor connected to the power take-01f arbor of the driving device by an elastic torque-transmitting element, the said rotor being controlled by the vibrating element through the medium of a pawl and ratchet device, the Whole in such manner that, as long as the torque applied to the rotor is below a given value, the vibrations of the vibrating element cause rotation of the rotor through an angular value greater than the pitch of the said Pawl and ratchet device, so that the rotor then advances step by step, whereas, when the torque transmitted reaches the said given value, the amplitude of the angular movement of the rotor produced by each vibration of the vibrating element is less than the said pitch, so that the rotor then performs an oscillating movement.

The drawing shows, by way of example, one embodiment of the invention.

FIGURE 1 is a diagrammatic plan view of a tuningfork driving device applied to the drive of the escape wheel of a timepiece;

FIGURE 2 is a view of a detail of FIGURE 1 on a larger scale, and

FIGURE 3 is a section on the line III-HI of FIGURE 2 drawn on a larger scale.

The driving device shown comprises a tuning-fork formed of two flexible strips 1 fixed to a yoke 2. The device ensuring the maintenance of the vibrations of the strips 1 is not shown in detail, since such device does not form part of the present invention. Briefly however, such device is constituted by a transistorized electronic circuit 3 comprising two coils 4, one being a driving coil and the other a pickup coil, which cooperate with two permanent magnets 5 carried by the ends of the strips 1.

One of the strips 1 carries a flexible element 6 forming a pawl, the free end of which acts on ratchet toothing comprising saw-tooth shaped or asymmetrical teeth 7 formed at the periphery of a rotor 8 coaxial with the power take-oif arbor of the driving device, this arbor being designated by the reference 9. In the example described and shown, the said arbor is constituted by the arbor of the escape wheel, designated by the reference 10, of a timepiece having a lever or anchor 11 and a balance wheel 12.

Connection between the rotor 8 and the arbor 9 is maintained by means of a spiral torque-transmitting spring 13 fixed at its outer end to the stud 14 carried by the rotor 8 and at its inner end to a collet 15 forced on to the arbor 9.

The device operates in the following manner:

At each vibration or oscillation, the tuning-fork sets the rotor 8 in motion, supplying a certain amount of energy to it through the medium of the pawl 6. The amplitude of the rotation of the rotor depends, on the one hand, on its inertia, which is constant, and on the opposing torque exerted on it by the spiral spring 13. The arrangement is such that, as long as the opposing torque is below a predetermined critical value, the amplitude of the angular movements of the rotor which are produced by each vibration of the tuning-fork is greater than the pitch of the toothing 7, so that the rotor advances step by step, winding the spring 13. On the other hand, as soon as the said opposing torque exceeds the critical value, the amplitude of the movements of the rotor is smaller than the pitch of the toothing 7, so that the rotor turns in the reverse direction under the action of the spring 13 during the return movements of the pawl. The rotor then performs an oscillating rotary movement, without winding the spring 13 any more. As soon as the opposing torque falls below the critical value, the winding of the spring 13 is resumed.

It is to be noted that the torque transmitted does not depend on the spring 13, but essentially on the inertia of the rotor 8.

In its horological applications, the present device enables the mainspring of a clockwork movement to be replaced by an electric driving device and even makes it possible to convert existing clockwork movements easily.

Thus, FIGURE 3 shows that such a conversion can be effected very simply by extending the arbor of the escape wheel beyond the normal outline of the calibre, shown at 16 in chain-dotted lines. A bush 17 on which the hub 8a of the rotor 8 is mounted for rotation is driven into a bar 18 of the frame of the calibre and, by means of a portion 17a, serves at the same time as a bearing for the extending portion of the arbor 9.

The present driving device is inexpensive to manufacture, even for the purpose of horological applications, since the properties of isochronism of the tuning-fork do not play any part in the operation thereof.

It is to be observed that the invention is not restricted to the case in which the virbrating element of the driving device is constituted by a tuning-fork.

What is claimed is:

1. A driving device comprising a vibrating element having vibrations which are maintained electrically, a power take-01f arbor, a rotor for driving said arbor, and drive means including a windable spring element coupled to said rotor and resisting rotation thereof, said spring element being coupled to the arbor transmit drive from the rotor to the arbor, and a ratchet and pawl device connecting the vibrating element with the rotor to transmit drive therebetween, said drive means causing the rotor to rotate step-by-step through an angular value greater than the pitch of the ratchet and pawl device until the spring element has been wound to a predetermined resistance whereupon the rotor is then driven in oscillation alternately by the vibrating element and the spring element through an angular movement which is less than the pitch of the ratchet and pawl device.

2. A device as claimed in claim 1 wherein said vibrating element is constituted by a tuning-fork.

3. A device as claimed in claim 1 wherein said power take-off arbor is constituted by the arbor of an escape wheel of a timepiece.

4. A device as claimed in claim 1 wherein said rotor is coaxial with the said power take-01f arbor, said spring element being a spiral spring having ends which are respectively fixed to the said arbor and to the said rotor.

5. A device as claimed in claim 1 wherein said ratchet and pawl device comprises a flexible strip connected to the vibrating element and constituting a pawl, and a ratchet wheel integral with the said rotor, said pawl having a free end engaged with said ratchet wheel.

6. A device as claimed in claim 5 wherein said ratchet wheel has saw-tooth shaped asymmetrical teeth disposed at the periphery of the rotor.

References Cited UNITED STATES PATENTS Warren 5841 Kercher 5841 Lavet 5823 Hetzel S8-39.5

RICHARD B. WILKINSON, Primary Examiner.

10 GERALD F. BAKER, Examiner. 

1. A DRIVING DEVICE COMPRISING A VIBRATING ELEMENT HAVING VIBRATIONS WHICH ARE MAINTAINED ELECTRICALLY, A POWER TAKE-OFF ARBOR, A ROTOR FOR DRIVING SAID ARBOR, AND DRIVE MEANS INCLUDING A WINDABLE SPRING ELEMENT COUPLED TO SAID ROTOR AND RESISTING ROTATION THEREOF, SAID SPRING ELEMENT BEING COUPLED TO THE ARBOR TRANSMIT DRIVE FROM THE ROTOR TO THE ARBOR, AND A RATCHET AND PAWL DEVICE CONNECTING THE VIBRATING ELEMENT WITH THE ROTOR TO TRANSMIT DRIVE THEREBETWEEN, SAID DRIVE MEANS CAUSING THE ROTOR TO ROTATE STEP-BY-STEP THROUGH AN ANGULAR VALUE GREATER THAN THE PITCH OF THE RATCHET AND PAWL DEVICE UNIT THE SPRING ELEMENT HAS BEEN WOUND TO A PREDETERMINED RESISTANCE WHEREUPON THE ROTOR IS THEN DRIVEN IN OSCILLATION ALTERNATELY BY THE VIBRATING ELEMENT AND THE SPRING ELEMENT THROUGH AN ANGULAR MOVEMENT WHICH IS LESS THAN THE PITCH OF THE RATCHET AND PAWL DEVICE. 